Biuletyn Instytutu Spawalnictwa No. 01/2012

extreme, the process was less stable, repeatability
was lower, and spatters became bigger,
which significantly deteriorated the aesthetics.
Another purpose of the research was to
investigate the impact of EN ratio on the course
of a welding process as well as on the quality
and aesthetics of welded joints. The plates
used for the tests were 1.5 mm thick, made
of steel grade DX 53 D ZF 100 RBO and provided
with a zinc-iron protective coating. The
tests involved the production of overlap joints
for various parameter settings and in constant
welding conditions (filler wire feeding rate
and welding rate). During the process, assessment
was connected with the process stability.
After the completion of the process, each
joint underwent a visual inspection. The criterion
used in the evaluation of the selection
of parameters and welding conditions was the
quality level B according to standard PN-EN
ISO 5817 [8]. Another process-related criterion
was the smallest possible damage to the
zinc-iron layer. A visual inspection of joints
produced at various settings of EN ratio revealed
that practically in the whole range of
EN ratio settings (except for extreme ones) it
is possible to obtain joints
of a very good quality. The
smaller the EN ratio in the
course the greater the damage
to a zinc-iron layer
near a weld. A decrease in
EN ratio resulted in an increase
in heat supplied to
the material being welded
which was manifested by
an increased width of the
joint overheating-affected
area, greater deformations,
and local burn-throughs of
elements being joined.
NR 01/2012
BIULETYN INSTYTUTU SPAWALNICTWA
Technological tests of welding of various
steels with protective coatings
The next stage involved technological tests
related to the welding of various joints (butt,
T-shaped and overlap joints) made of plates of
various thicknesses. Tests revealed that MAG
welding with variable polarity current makes
it possible to obtain butt, T-shaped, and overlap
joints characterised by very good quality.
Apart from technological parameters, the basic
variable affecting the possibility of joining
elements and the course of a welding process
is the EN ratio. Welding of thin elements is
most advantageous if accompanied by a high
EN ratio as it translates to small deformations
and minimum damage to the zinc-iron layer. In
turn, T-shaped and butt joints of greater thicknesses
should be welded with a lower EN ratio
as the process of welding is more “energetic”
(i.e. heat input is higher). According to the test
results, the appropriate selection of technological
parameters makes it possible to produce
overlap and butt joints of plates having as little
as 0.75 mm and 0.8 mm thicknesses. Figures
8-10 present selected joints and their macrostructure.
Fig. 8 General view and macrostructure of overlap joint of 0.75mm-thick steel
DX56D ZF100 RBO; etchant: Adler, magnification x8
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